Lifting the lid on 50 year old tins

For over 50 years, Eric D. Pritchard meticulously collected and catalogued New Zealand insects. His astonishing and beautiful collection featured thousands of beetles painstakingly arranged on cards with a home-made glue and stored carefully in metal cigarette tins; some for almost 90 years.

Time has taken its toll, and conservation work was required to preserve and stabilise this special collection so it could be photographed for the AM Collections Online database.

Why is the collection special?

The collector and creator of this unique collection of predominantly New Zealand Coleoptera was Eric D. Pritchard. Pritchard was a primary school teacher and collected beetles as a hobby from the 1930s to the 1980s.

He was very good with his hands and had a love for detail - as a result, this collection is delightful, beautiful and scientifically valuable.

It’s unusual to find insects stored in metal cigarette tins in such a careful and neat manner, adhered closely together on card with home-made glue. Accompanying each of the 25 tins is a notebook containing data on every insect within.

Recorded are the species name, where and when the insect was found and what the weather conditions were like on that day.

Such clear records of where these New Zealand insects used be to found shows us how habitats have changed over time and means that this collection has remarkable scientific value.

The conservation challenge

Beetle in middle during cleaning under microscope, left side of body already cleaned.

There is a lot happening in these tins. From a conservation point of view, we are dealing with corroded metal tins; acidic and stained card; acidic, yellowed, brittle and crumbly glue; surface dust, ingrained dirt, and possibly aged pesticides.

And last, but not least, partially degraded insects. Some beetles have already become detached from the card while others are missing legs, heads, or antennae.

What can be done?

Taking the age and combination of materials into account, the current condition of the insects wasn’t too bad. Most of the chemical and physical reactions had already happened. Therefore, it became a matter of preserving and improving their condition by reducing dirt, dust, corrosion products, and other residues both on the card and on the insects themselves (those that were stable enough to withstand treatment).

To avoid loss of information about species, it was important to glue back loose insect parts if they could be accurately re-located.

It is important to think about any preventive measures we can take to reduce the risk of further damage and to minimise degradation processes. In the case of this collection, the greatest risk was in the insects’ storage.

The insects that are glued onto the lid of the cigarette tins are hanging down when the lid is closed. This increases the risk of the beetles falling off their cards. The acidity of the paper and glue in an enclosed environment like the tins might also cause further degradation and corrosion, particularly if there’s an increase in humidity.

With this in mind, it’s good to know that the tins are being accessed twice a year to monitor their condition and any signs of change. In addition, Conservators have recommended that the notebook be digitised to future-proof all that valuable information.

How is it done?

Every intervention puts the insects at high risk of damage to the bodies or to losing body parts - and with that comes the loss of valuable information associated with them.

It was John Early, Curator Entomology, who made a very helpful comment in regards to the conservation work: ‘less is more’.

One tin with very fragile flies where mould had grown on their bodies was simply too risky to attempt to remove it. The conclusion that had to be drawn was: sometimes doing nothing is the best option.

For the remainder, in order to clean the various surfaces, we had to think of micro-scale options to be able to reach the small spaces between insects, legs, antennae and so on. The task was undertaken using a very fine brush, a glass pipette attached to the end of the vacuum hose...and minimal suction!

The conservator in charge of cleaning the Collection also had to control their breathing, ensuring their shallow breaths above the tiny specimens didn't disturb any loose parts.

More ingrained dirt was reduced using demineralised water and ethanol. Dentist tools and micro tweezers were very helpful for handling the beetles while adhering them back onto the card.

Working under the microscope made the conservation work accurate. Even so, it took a bit of practice to glue insects onto card!